Why buy a commercial chocolate sauce when it's so easy to make your own? Most supermarket products pale in comparison to this homemade version, which is quick and easy to make. Choose a high-quality chocolate for best results. The hot fudge sauce will keep, covered, in the refrigerator for up to 1 month.
Place the chocolate and butter in a small saucepan and set over low heat to melt, stirring occasionally until smooth.
Add the evaporated milk and confectioner's sugar, and stir to combine. Cook over medium heat, stirring frequently, until the sauce thickens, 7 to 10 minutes.
Remove the pan from the heat and stir in the vanilla. If not using immediately, reheat the hot fudge sauce very slowly over low heat.